Abstract

The effects of hydroxylamine and tyrosine on homogenates
of early Drosophila pupae have been studied by several criteria.
Both low speed and high speed supernatants of the
homogenized pupae give positive tests for hydroxamic acids
after incubation with hydroxylamine. A comparison of the
hydroxamic acid forming abilities of the supernatants shows
that the low speed supernatant is the more active and that
tyrosine increases hydroxamate formation in the low speed
but not in the high speed supernatants.

Both hydroxylamine and tyrosine have definite effects
on alkaline phosphatase activity in the low speed supernatant.
Tryosine causes an increase in the activity upon incubation
at 0°C and 25°C. Hydroxylamine decreases the activity regardless
of the temperature or the presence of tyrosine.

Both tyrosine and hydroxylamine affect the distribution
of ninhydrin-positive compounds of dialyzates of low speed
supernatants. Hydroxylamine effectively reduces the amount
of the acidic components, but its effect is slightly modified
by tyrosine. The presence of tyrosine alone increases the
amount of acidic materials as compared to the untreated sample.
In general, the ninhydrin-positive compounds are more sensitive
to the presence of hydroxylamine than of tyrosine.

Some preliminary work on the nature of the compounds in
question shows that they contain more than one amino acid.
The data on the nature of these compounds is consistent with
the proposition that peptidyl hydroxamates are the Fe ^(+++)-
positive materials.

Naturally-occurring peptides and the current understanding
of protein synthesis are reviewed. The possibility that
peptides per se are incorporated into the proteins in Drosophila
pupae is discussed and mechanisms for this possibility
are explored.